Telephone system



Nov. 29, 1932. v. s. THARP TELEPHONE SYSTEM v. s. THARP 1,889,229 TELEPHONE SYSTEM Filed Jan. 2:5. 1931 4 Sheets-Sheet 2 Nov. 29, 1932.

` Imm-:F 1cm* E. TharF NOV. 29, 1932. V, s THARP 1,889,229

TELEPHONE SYSTEM Filed Jan. 23. 1931 4 Sheets-Sheet 3 Nov. 29, 1932. v. s, THARP 1,889,229

TELEPHONE SYSTEM Filed Jan. 23. 1931 4 Sheets-Sheet mi373 `wln'lq/ 4 E [3M Sg u 'h Mg ".1 l 13751.- T gg 'i ig T GEM Tfk gg T 12M/Nr RING. [All` GEN F11, l E' 573,

PRH-3 RIMS. /NZ' GEM I Patented Nov. 29, 1932V UNITED STATES PATENT orifice;

VICTOR S. THARP, OF .'ELMHURST, ILLINOIS, ASSIGNOR, BY MESN-ASSIGNMENTS, T

ASSOCIATED ELECTRIC LABORATORIES, IN C., OF CHICAGO, ILLINOIS, A CORPORATION OF DELAWARE TELEPHONE SYSTEM Application filed January 23, 1931. Serial No. 510,680.

The present invention relates in general to automatic telephone systems, and its object, broadly stated, is to provide new and improved automatic switching apparatus of the step-by-step type.

' More specifically, the object of the present l invention is` the provisionof a new and improved pulsing scheme for positioning automatic switching apparatus.

A further object is the provision of a new and improved 20G-line connector. The new switch is of the twenty-level type using two sets of wipers the set toV be used is determined by the first digit dialled into the switch.

A further object is the provision of a new and improved 20G-line frequency selecting connector switch.. The first digit dialled into the'switch determines the set of wipers, the ringing frequency, and the side of the line over which the ringing current is to be transmitted.

A further object is the provision of a new and improved selector circuit performing all necessary and standard operations with four relays instead of the five relays required heretofore.

A still further object is the provision of a new busying circuit arranged to signal the calling subscriber to indicate that the line is busy when the connector comes to rest on a busy line. The busy relay is a two-step relay arranged to be energized in its first step to close one set of contacts only when the test wiper of the switch passes over busy lines, and to energize all the way only when the test wiper comes to rest on the busy line.

The foregoing objects and features t0 gether with others not specifically mentioned at this time will be further discussed in connection with the detailed description of the operation of the various circuits.

The accompanying drawings comprising F igs. l to 7, inclusive, show bymeans of the usual circuit diagrams a sufficient amount of equipment in atelephone system embodying the invention to permit it to be readily described and understood., In order for the drawings to be understood best, Fig. 2 should be placed to thevright of Fig. l with the interconnecting lines in alignment; and Fig. 3

should be placed beneath Fig. 2. Figs. 4, 5, 6, and 7, are schematic drawings showing vafy rious methods for wiring the bells to the line for party line ringing. They will be described in connection with Fig. 3.

Fig. l shows a lineswitch LS, which is one of a plurality of lineswitches controlled by a master switch MS (partially shown) similar to that disclosed in the Voss Patent No. 1,809,086,granted June 9, 1931, and having access to a plurality of selectors, one of which is the selector S. Mechanically, selector S is of the usual vertical and rotary type of switch having its bank contacts arranged in horizontal rows or levels. The selector S has access to a plurality of groups of connectors (ten groups" or less), of which connectorC, Fig. 2, is one of the connectors in one group', and connector Cl, Fig. 3, is one'of theconnectors in another group. The selector S is of the so-called battery-searching type of switch wherein it must find battery potential over wiper 128 before it will cut in on the idle trunks.

Y Fig. 2 shows a 20G-line, E20-level, connector C whose wipers 257-259, inclusive, are used to complete the connection over one set of banks when the wiper switching relay is not energized. The wipers; QSO-262, inclusive,

are used to complete the connection over the other set'of banks when the wiper-switching relay is energized.

` Fig. 3 shows a 20G-line, .QU-level, frequency selecting connector Cl which is one of the connectors accessible to selector S, Fig. l, over a particular level. The first digit dialled into the switch operates the auxiliary switch AS to select the ringing free tacts. Subscribers Bl-B5, inclusive, are selectively signalled when the normally con- Arent generators similar to generator GENV lil nected set of wipers of connector C1 are connected to the party lines and subscribers B6- B10 are selectively signalled when the normally disconnected set of wipers of connector C1 are connected to the party line. The conductors designated FREQl to FREQ, inclusive, all extend to vseparate ringing curandthe generators are, all ofv different frequencies. inclusive, represent the switch jack terminals of the connector C1, to which the live different ringing generators are connected. The ringers connected to the party lines each respond to a differentv ringing current frequency, which is in accordance with the well known practice of harmonic signalling.

Fig. 5 shows a lO-party line which is accessible tothe same group of frequency selecting connectors as the two -party lines shown in Fig. 4, one of which is connector C1 shown in Fig. 3, over a group of contacts of their associated bank contacts. The subscribers l(ll-C10, inclusive, are all connected to one party line which terminates in the bank contacts which are accessible over the normally connected set of wipers of the connector and are multipled to the bank contacts which are accessible over the normally disconnected setof wipers. When the normally connected set of wipers are used subscribers (l1-C5, inclusive, are selectively signalled and when the normally disconnected set of wipers are used subscribers Gti-G10, inclusive, are selectively-signalled. The different ringing current generators are wired to the switch jacks of thev connector switch as is shown to the left of4 Fig. A5 which is eX- actly the same as is shown in Fig. 4. 'With the party line connectors wired in this manner the saine group of switches can be used for selectively signalling both five and tenparty line subscribers.

Fig. 6 shows two S-party lines which are accessible to a group of frequency selecting connectors having the different ringing current conductors wired to the switch ack terminals of the connectors, as is shown to the left of Fig. 6. For this type of service only three different ringing current frequencies are required.

The three party lines shown in Fig. 6,' are accessible to a group of frequency selecting connectors, which are similar to the connector C1 shown in Fig. 3, except that the switch jack terminals of the connectors are wiredv as shown to the left of Fig. 6. In establishing connections to subscribers D1, D8, and D5 the normally connected set of wipers of the connector is used and in establishing connections with subscribersrD, D8, and D10 the normally disconnected set of wipers is used. It should be noted that for three -p arty service the ringers of the subs-tations are The switch jack terminals 1 to 5,`

bridged across the conductors of the party line.

Fig. 7 shows two 5-party lines which are accessible to the same group of frequency selecting connectors as the two S-party lines shown in Fig. 6. llVith the switch jack terminals of this `group of frequency selecting connectors wired as is shown to the le'lt of Fig. 7 the live subscribers F11-E5, inclusive, may be selectively signalled when the normally connected set of wipers of any one of the connectors is associated with the bank contacts to which conductors 77 3 and 775 of the party line are connected and subscribers E6-E10, inclusive, may be selectively .signalled whenthe normally disconnected set of wipers is associated with the bank contacts to which conductors 7 63 and 7 G5 of the party line are connected. 1t should be noted that the saine group of frequency selecting connectors can be used for selectively signalling subscribers on either 3 or -party lines. Y

The present system, having been described in general, will nowbe described in connection with a detailed description of the operation of the apparatus shown in the drawings. For this purpose it will be assumed thattlie subscriber at substation A, Fig. 1, desires to converse with the subscriber at substation A2, Fig. 2, whose telephone number is 3234.

`lllhen the receiver is removed at substation A, a circuitis closed across line conductors ,11 and l'for the line relay 14 through contacts of the bridge-cut-oif armature 15 of the lineswitch'LS. Relay 14 operates and disconnects the so-called private-normal conductor 13 from the bridge-cut-oc (upper) winding of the lineswitch magnet 16 and connects it to ground, thereby guarding the calling line against seizure by connectors having access to it. At armature 17 and its front contact, relay 14 closes a circuit for the pulldown (lower) winding of magnet 16 over the associated chain conductor 19 which is grounded at the master switch, and at the same time it opens the chain as regards the succeeding lin-eswitclies. lt will be noted that ground potential is supplied to the chain conductor 19 through the contacts of the open chain relay, start relay and lower winding of the delay relay in the master switch MS.

It may be pointed out that the delay relay is included in the circuit to delay the operation of the lineswitch for a slight interval following the operation of the Vline relay 111. This will give a releasing lineswitch time for the plunger to re-alignitself before the li neswitch can be reoperated. The current flow through the pull-down winding over the chain circuit is not suicient to operate either of the armatures of the magnet 16 as long as the lower winding of the delay relay is in the circuit alone. The upper winding of the delay relay, it will be noted, is normally short-cirlOO Lessines cuited through its own contacts. Due to the fact that the short-circuited winding is on the armature end of the relay, it is slow-to-energize. l/Vhen the delay-r-elay operates, it removes the short circuit from around the upper winding and connects the low resistance upper winding in parallel with the high resistance lower winding, allowing suflicient current to flow over the chain conductor 19 to operate. both armatures of the lineswitch magnet 16. The bridge-cut-oii" armature 15 operates the associated contacts to disconnect ground and lin-e relay 14 from the conductors of the calling line,andthe plunger armature 20 operates the bank springs 21-24 and also closes contacts 25. rlhe closing` ofcontacts 25 reconnects the upper winding of magnet 16 to the grounded conductor 13. Line relay 14, being slow-acting, remains operated for an interval.

When the contact springs 21-24 are pressed into engagement with their respective associated contacts to lextend the connection to the selector S, the ground potential maintained on conductor 13 by the slow-acting line relay 14 is extended to the release trunk conductor 134 and over the branch conductor 136 to the master switch bank (not shown). Ground on the master switch bank causes the master switch to preselect another idle trunk to selector similar to selector S.

The lineswitch also completes a circuit at contact springs 21 and 24 and their associated contacts for energizing the line relay 101 of the selector S as follows: From battery, upper winding of line relay 101, armature 121 and its resting Contact, conductor 1331 contact spring 21 and associated contact of the linesivitch, line conductor 11, subscribers loop, line conductor 12, contact spring 24 and associated contact of the lineswitch, conductor 135, armature 125 and its resting contact, lower winding of line relay 101, normally closed contacts of overflow springs 130, one

' side of the dial tone transformer to ground.

Upon energizing, line relay 101, at the normally closed contacts controlled by armature 108, removes the normal shunt around the upper winding of release relay 102 and at thesame time it closes a circuit for both windings of release relay 102 in series with the lower winding of series relay 103, from ground, normally closed contacts of the vertical oft-normal springs 116, normally closed contacts controlledby armature 112, upper winding of release relay 102, armature 108 and its front'contact, lower winding of series relay 103, lower winding of release relay 102, to battery. Release relay 102 energizes over this circuit and at armature 112 and its front contact substitutes a locking ground for the original energizing ground at the vertical oil-normal springs 116.

As a further result-of itsoperation, release relay 102 opens a point in the circuit of the release magnet 107 at armature 110 and its resting contact, at armature 114 and its front contact it prepares a circuit for the rotary magnet, and at armature 113 and its front contact it places ground potential on the release trunk conductor 134 to maintain the lineswitch LS operated through the upper winding of magnet 16 after line relay 14 has fall-en back, to busy the calling line in the connector banks over con-ductor 113, and to busy the trunk to switch bank over conductor 136.

lt may be pointed out that the circuit for release relay 102 included the lower winding of series relay 103 which however does not operate. However, when release relay 102 energizes it closes a circuit at armature 111 and its front contact from ground at the normally closed contacts 116'of the vertical olfnormal springs VON to thev upper winding of series relay 103 and the lower winding of release relay 102 in series. Series relay 103 energizes, due to the current flow over both of its windings, preparing the circuit for the vertical magnet 105 at armature 115 and its front contact and opening a point in the circuit to the rotary magnet 106 at armature 118 and its resting contact. I

t should be noted that the original energizing circuit for release relay 102 includes ground at the normally closed contacts of the Vertical olii-normal spring. lt sometimes happens that a selector becomes stuck mechanically and does not restore and consequently the vertical off-normal springs remain in an operated position. Due to the way in which the master switch tests the bank contacts to which the release conductors, similar to release conduct-or 136, are connected, it will stop on a selector that is not in `its normal position, if there is an absence of Vground potential on the release conductor thereof. lVith the selector in an olf-normal position it will be seized by a lineswitch such as lineswitch LS. However, when this happens, the release relay 102 does not operate, owing to the fact that the circuit is not completed at the vertical oil-normal spring 116 andv the lineswitch LS releases for the want of holding potential on conductor 134. The lineswitch will release, and due to the fact that it is a self-aligning lineswitch, the plunger will align itself with the shaft controlled by the master switch and will seize a newly-selected idle trunk to another selector.

The vcircuit of the line'relay 101 includes one side of the dial tone transformer 192, as has been Vhereinbefore described, and the tone produced by the dial tone current is heard by the calling subscriber, indicating that he jnay now dial the digits of the desired numer. Y

When the digit 3 is dialled,-the circuit of the line relay 101 is opened three times at the selector S in the master Y ile 6o gized during pulsing to complete the enen calling station by means of the usual calling device (not shown). Each time the line relay 101 falls back after its circuit is opened, it closes a circuit to the vertical magnet 105 at armature 109 and its resting contact, and opens the circuit including the lower winding olf series relay 103 at armature 108 and its front contact. Line delay 101 also places a short circuit around the upper winding of the release relay 102 at the normally closed contacts controlled by armature 108, and by the same action closes a circuit for the upper winding of series relay 103 and the lower winding of the release relay 102 in series as follows: from ground, armature 112 and its front contact, normally closed contacts controlled by armature 108, armature 117 and its front contact, contacts 137 of the Vertical ofinormal springs VON (closed on the first vertical step), armature 111 and its iront contact, upper winding of series relay 103, lower winding of release relay 102, to battery. Series relay 103 remains energized over this circuit. The current flow through the lower winding of release relay 102 is insufficient to keep the relay energized, however, together with the shunt around the upper' winding it makes the relay slow to release. The release relay 102 reina-ins energized throughout the series of impulses. Each time line relay 101 energizes following the iirst deenergization, a circuit is closed to both windings of release relay 102 in series with the upper winding of series relay 103 and'both windings of relay 102 in series with the lower winding ot series relay 103. Relay 102 is fullyl energized over this circuit and the amount of current flow over both windings of series relay 103 is insufficient to keep the relay energized, however, it makes the relay slow tov release.

By way of an explanation, the iirst time line relay 101 energizes, release relay 102 also energizes and causes series relay 103 to energize. The lirst deenergization of line relay 101, during 'impulsing, causes the vertical magnet to step the wipers up one step, Opening contacts 116 and closing contacts 137 ot the vertical o-normal springs VON. Line relay 101 also places a. shuntJ around the high resistance upper winding of release relay 102 and by the same action it completes a circuit for the high resistance upper winding of series relay 103 in series with the low resistance lower winding of release relay 102. The shunt around the upper winding and the current flow in the lower winding of relay 102 is just suilicient to keep the relay energized until the line relay is again energizing circuit Jfor the yrelease relay. The

release relay 102 does not deenergize during pulsing. When the line relay 101 energizes again after the rst deenergization, the high and low resistance windings of release relay 102 are included in the circuit of the lower winding of series relay 103 over one path, and the upper winding of series relay 103 in the other path. The amount of current flow in release relay 102 is sufficient to keep the relay energized, but the current llow in series relay 103 is only sui'licient to make the relay slow-to-release. The series relay 103 is maintained energized during impulsing.

As has been mentioned hereinbe'fore, the circuit of the line relay 101 has been opened three times by the calling subscriber, and each time a circuit has been completed to the vertical magnet 105. By the operation ot the vertical magnet 105 the wipers 127- 129 ot the selector S are operated step-bystep until they are opposite the third level of the switch bank. The circuit of the line relay 101 and release relay 102 are the same as has been hereinbetore described, and they remain energized. The circuit for each wind# ing ot series relay 103 includes both windings oi release relay 102 as has been described. both windings of series relay 103 is only suiiicient to make the relay slow to release, and it subsequently restores to normal. Upon restoring to normal series relay 103 opens the part of the circuit of release relay 102 which includes the upper winding of series relay 103 at armature 117 and its front contact, however, release relay 102 remains energized, from ground, armature 112 and its front Contact, upper winding of re lease relay 102, armature 108 and its front contact, lower winding of series relay 103, lower winding of release relay 102, to bat tery. As a further result of the falling back of series relay 103, the circuit to the vertical magnet 105 is opened at armature 115 and its front contact. and at armature 118 and its resting contact it closes a circuit to the sell`-i1iterrupting rotary magnet 106. rEhe self-interrupting circuit for the rotary magnet 106 is as follows: from ground, armature 113 and the front contact on release relay 102, contacts 119 of the vertical offln this circuit the current flow in n normal springs'VON (closed onfthe iirst vertical step), armature 114 and its front i contact, armature 118 and its resting Contact, normally closed contacts 120 of the overflow springs 0F, armature 124i and its resting contact, self-interrupting contacts and winding oi the rotary magnet 106, to battery. By the buzzer-like operation of the rotary magnet 106, the wipers 1273129 are driven over the contacts of the bank in the third level, or any other level that is selected by the calling subscriber.

l.Vhen an idle contact set is reached (for example, the contact set from which the conductors 13S-140 extend to the connector C), a battery potential is encountered on the test contact thereoi3 by wiper 128, the conductor 139 of connector C being connected to battery through armatures 220, 244, and 256 and their respective resting contacts.

When this battery potential is encountered by test wiper 128, the switching relay 104, whose upper winding is connected between grounded conductor 134 and the test wiper 128, energizes. Upon energizing, relay 104 opens the circuit of the rotary magnet at armature 124 and its resting contact, locks itself over its lower winding in series with the rotary magnet 106 at armature 124 and its front contact from grounded conductor 134, and opens a point in the circuit ot' the release magnet 107 at armature `122 and its front contact. Relay 104 also extends conductor 134 through to wiper 128 at armature 123 and its front contact, short-circuiting its upper winding at the sam-e time, it disconnects the incoming conductors 133 and 135 from the windings of the line relay 101 at armatures 121 and 125 and extends them through the wipers 127 and 129, conductors 138 and 140, normallyy closed contacts controlled by arma tures 215 and 216, upper and lower windings of line relay 202 ofthe connector C to battery and ground, respectively.

In case the selector S :tails to find an idle trunk line and continues to rotate until the wipers 127-129 pass beyondthe last set 'of banlr contacts, contacts 120 and 130 of the overflow springs OF are operated. Contacts 120 of the overliow spring OF open the selfinterrupting circuit to the rotary magnet 106 to stop further rotation of the switch, and contacts 130 of the overflow springs OF substitute busy tone current from the busy-tone transformer 131 for the dial-tone curr-ent through the dial-tone transformer 132. l/Vhen the calling subscriber hears the busytone from the busy-tone transformer 131,' he replaces his receiver. When this occurs line relay 101 falls back and places a shunt-.around the upper winding of release relay 102 at the normally closed contacts controlled by armature 108. Due to the shunt around its upper winding, release relay 102 is made slowto release, and subsequently restores to normal. Upon falling back, release relay 102 closes a circuit to the release magnet 107 from ground, `armature 110 and its resting contact, armature 122 and itsV resting contact, contacts 126 of the vertical ol-normal springs VON (closed on the first vertical step) winding of release magnet 107, to battery. Release magnet 107 energizes and the switch restores to its normal position. The lineswitch LS releases inthe usual manner when the ground potential is removed from conductor 134.

Then the -level connector C is seized by the selector S over conductors 138 and 140, line relay 202 energizes over the previously traced circuit. Upon energizing, line relay d 202 removes the shunt around the upper winding of release relay 203 at the normally closed contacts controlled by armature 217 and at the same time it closes a circuit for both windings of the release relay 203 in series with the lower winding of series relay 204, from ground, upper winding of release relay 203, armature 217 and its front contact, lower winding of series relay 204, lower winding of release relay 203, to battery. Release relay 203 energizes over this circuit and at armature 222 and its front contact it closes a circuit for the upper winding of series relay 204 1n series with both of its windings. However, due to the fact that the high resistance upper winding of release relay 203` is in series with both of the windings of series relay 204, it does not energize.

As a further result of its operation release relay 203 opens a point in the circuit of the release magnet 210 at armature 219 and its resting contact, at `armature 223 and its front contact it prepares the impulsing circuit, and at armature 220 and its front contact it places ground potential on the release trunk conductor 139 to maintain the switch through relay 104 of the selector S energized after the subsequent release of the release relay 102 due to the deenergization of the line relay 101, and also to maintain the ground potential on the release trunk conductor 134. This switch is now prepared for dialling.

rlhe calling subscriber now manipulates the.

calling device in accordance with the second digit in the telephone number of the wanted subscribed. lVhen the second digit is dialled, which in this case is the digit 2, the circuit of the line relay 202 is openedV two times at the calling station. Each time the linerelay 202 falls back it places a short circuit around the upper winding of release relay 203 at the normally closed contacts controlled by armature 217, and by the same action it closes a circuit for the upper winding of series relay 204 in series with the lower winding of release relay 203 as follows: from ground, normally closed contacts controlled by armature 217, armature 222 and its front contact, upper winding of series relay 204, lower winding of release relay 203, to battery. Series relay 204 energizes over this circui The current low through the lower winding of release relay 203 is insufficient to keep the relay energized, however, together with the shunt around the upper winding the relay is made slow-torelease, The release relay 203 remains energized throughout the series of impulses.

Each time line relay202 energizes following the first deenergization, a circuit is closed to both windings of release relay 203 in series with the upper winding of series relay 204 and both windings of release relay 203l in series with the lower winding of series relay 204. Release relay 203 is fully energized again over this circuit. The current flow overboth windings of series relay 204 is insufficient to keep the relay energizedhowever, enough current Hows to make the relay slow-to-release. Series relay 204 remains energized during each series of impulses, but subsequently deenergizes after the line relay remains in an energized position.

By way of an explanation, the first time line relay 202 is energized, release relay 203 is also energized. The first time line relay 202 deenergizes, during impulsing, series relay 204 energizes. Release relay 203 and lseries relay 204 both remain operated during the seriesof impulses. After impulsing, line relay 202 remains in its energized position, release relay 203 remains energized, and series relayv 204 subsequently deenergizes.

The first time line relay 202. falls back, during impulsing, it closes a circuit from ground, armature 218 and its resting contact, armature 223 and its front contact, armatures 241, 249, and 230 and their respective resting contacts, contacts 235 of the vertical off-normal springs VON, armature 236 and its resting contact, lower winding of two-step relay 206,.to battery. Two-step relay 206 energizes in its first step, closing contacts A only, to prepare a locking circuit for itself from ground at armature 221 and its front contact. It is obvious that the upper winding of two-step relay 206 is short-circuited by its initial energizing circuit and it cannot operate to its second step until the short circuit is removed. Line relay 202 subsequently energizes again as has been described hereinbefore, and opens vthe initial energizing circuit for two-step relay 206 at armature 218 and its resting contact'. The opening of the original energizing circuit for two-step relay 206 removes the short circuit from its upper winding, permitting the relay to energize to its second step over both windings in series to close all of its armatures from ground, armature 221 and its front contact, contacts A of relay 206, both windings of relay 206, to battery. Upon energizing to its second step, relay 206 prepares a circuit for combination switchover and ring-cut-oii relay 205 at armature 233 and its front contact, it prepares a circuit for the wiper-switching relay 209 at armature 236 and its front contact, and it prepares a locking circuit for relay 209 at armature 237 and its front contact.

The second time line relay 202 falls back, it again closes armature 218 and its resting contact to complete a circuit over the path )ust traced. This time the two-step relay 206 is energized and the circuit includes armature 236 and. its front contact, normally closed contacts controlled by armature 254, winding of wiper-switching relay 209, to battery. The wiper switching relay 209 energizes and locks itself at armature 254 and its front contact to ground at armature 237 and its front contact, and' by the same action it opens its initial energizing circuit from ground at armature 218. The wiper-switching relay 209 also connects up wipers 260-262 at armatures 252, 253,*and 255 and their respective front contacts.

After the first series of impulses has been transmitted, line relay 202 remains in an energized position. Series relay 204 subsequently releases, as has been hereinbefore described. Upon falling back, series relay 204 completes a circuit for the slow-acting combination switchover and ring-cut-off relay 205 from ground, armature 226 and its resting contact, contacts227 of the vertical ofi"- normal springs VON, armature 233 and its front cont-act, lower winding of relay 205, to battery. Upon energizing, relay 205 prepares a locking circuit for itself at armature 229 and its front contact and it prepares the circuit for the vertical magnet 211 at armature 230 and its front contact. The closing of armatures 228 and 231 and their respect-ive front contacts has no effect at this time.

The calling subscriber may now dial the third digit of the called number. When the third digit is dialled, which is in this case the digit 3, the circuit of the line relay 202 is again intermittently interrupted three times in response to the operation of the calling device by the calling subscriber. The first time line relay 202 falls back, series relay 204 energizes and remains in an energized position throughout the series of impulses as has been hereinbefore described. Upon energizing, series relay 204 opens the initial energizing circuit for the slow-acting combination switchover and ring-cut-off relay 205 at armature 226 and its resting contact, however, it also complet-es a locking circuit for relay 205 before it falls back from ground, armature 226 and its front contact, armature 229 and its front contact, lower winding of relay 205, to battery. As a further result of the falling back of line relay 202 a circuit is completed for the vertical magnet 211, from ground, armature 218 and its resting contact, armature 223 and its front contact, armatures 241 and 249 and their respective resting contacts, varmature 230 and its front contact, winding of the vertical magnet 211, to battery. Each time the line relay 202 falls back the circuit is completed to the vertical magnet 211 and by its operation the wipers 257-262, inclusive, are raised opposite the third level of bank contacts.

At the end of the vertical movement, the line relay remains energized and series relay 204 subsequently releases as has been described. Upon falling back, series relay 204 opens the locking circuit for the combination switchover and ringcutoif relay 205 at armature 226 and its front contact. Relay 205 subsequently releases due to the fact that its initial energizing circuit has been opened, by the first vertical step of the switch, at contacts 227 of the vertical off-normal springs VON. Upon the falling back, relay 205 prepares the circuit for therotary magnet 212 at armature 230 and its resting contact.

The calling subscriber now transmits the linal digit of the called telephone number, which is in this case the digit 4. Responsive to the interruptions of the line relay 202, series relay 204 is energized again and remains energized throughout the series of impulses. Each time line relay 202 falls back a circuit is completed for the rotary magnet 212 from ground, armature 218 and its resting contact, armature 223 and its front contact, armatures 241,249, and 230 and their respective resting contacts, contacts 2340i the vertical oit-normal springs VON (closed on the first vertical step of the switch), winding of the rotary magnet 212, to battery. By the operation of the rotary magnet the wipers 257-262, inclusive, are rotated step-by-step and are finally brought to rest in engagement with the particular set of bank contacts in which the line of substation A2, whose telephone number is 3234, is terminated.

rlhe series relay 204, in its operated position, connects the test wiper 261 to the twostep busy test relay 207. It any oi' the contacts the test wiper .261 passes over are busy, the conductor similar to conductor 264 is grounded, causing the two-step busy test relay 207 to be energized to its first step from ground (over a conductor similar to concluetor 264), testwiper 261, armature 253 and its front contact, normally closed contacts controlled by armature 245, normally'closed contacts controlled by armature 239, armature 225 and its front contact, armature 246 and its resting contact, resistance 232, winding of relay 207, to battery. rlhis relay is only momentarily operated to its first step and closes contact A at armature 240 only as the test wiper 261 passes over contacts of the busy lines. The operation ot the relay to its lirst step has no effect at this time because the circuit for energizing the relay to its second step is opened at the normally closed contacts controlled by armature 225 ot *he series relay 204. v

The final digit has now been received and the wipers of the connector have been placed.`

in connection with the terminals or the called line. It the line is busy, there will be a ground potential on the test conductor 264 and the above circuit is again completed for operating the busy test relay 207 to its iirst step before the series relay 204 falls back. Series relay 204 subsequently releases however, and at the normally closed contacts controlled by armature 225 it completes a circuit for energizing the busytest relay to its second step, from grounded conductor 264, wiper 261, armature 253 and its front Contact, normally closed contacts controlledby armatures 245, 239, and 225, armature 240 and its front contact A, winding of relay .207,` to battery. Upon energizing to its second step the busy test relay 207 opens the circuit for the rotary magnet 212 at armature 241 and its resting contact to prevent further rotation of the Wipers, locks itself to grounded conductor 139 at armature 239 and its front contact, at the same time opening its initial energizing circuit over the test wiper and it connects the busy tone conductor to the upper side of the line at armature 238 and its front contact. Ilhe subscriber, upon hearing the busy signal, will replace his receiver, thereby releasing the connector C and all previously operated switches.

Assuming now that the called line is idle when the connection is established, under these circumstances there will be no ground on conductor 264 and consequently the busy relay 207 will not be energized. Shortly after the last impulse of the series the series rela-y 204 falls back and completes the circuit for the slow-acting switching relay 208 from grounded conductor 139, armature 239 and its rest-ing Contact, lower winding of switching relay 208, armature 240 and its resting contact, normally closed contacts controlled by armatures 225, 239, and 245, armature 253 and its front contact, test wiper 261, conductor 264, and thence to battery by Way of the bridge-cutoff winding of the lineswitch magnet ot the associated lineswitch (not shown), which lineswitch may be the same as the lineswitch LS associated with the line of substation A. Responsive to the closure of this circuit the lineswitch magnet voi' the called lineswitch operates its bridge cut-on armature to disconnect the line relay of the lineswitch from across the line conductors thereat.

ln the connector. C the slow-acting switching relay 208 energizes over the above-traced circuit and at its lightly adjusted armature 247 closes a locking circuit for its upper winding, opens the circuit for the rotary magnet 212 at armature 249 and its resting contact, and places direct ground on the test wiper at armature 245 and its front Contact and by the same action opens its initial energizing circuit. Relay 208 also prepares a locking circuit for the combination switchover and ring-cut-oi relay 205 at armature 248 and its front contact, connects the ringbaclr tone conductor to the calling line at armature 242 and its frontcontact to indicate to the calling subscriber that the calling line is being signalled, and it connects up the line wipers 260 and 262 at armatures 243 and 251 and their respective front contacts. By the latter operation, `a signalling circuit is established whereby ringing' current from the generator GEN is intermittently projected over the called line to operate the bridged ringer at substation A2110 notify the called subscriber that he is wanted. rlhe return path for the ringing current includes the upper winding of the combinal tion switchover .and ring-cut-oi relay 205 and ground.

Vvvhen the called subscriber responds to the ringing of his bell by removing his receiver, a direct current bridge is closed across the associated line conductors 263 and 265 in the regular manner, whereupon the ringcut-oii relayT 205 energizes.

Upon energizing, the combination switchover and ring-cut-off relay 205 closes a locking circuit for itself at its lightly adjusted armature 229, disconnects the line wipers from its own upper winding and the generator lead at armatures228 and 231 and their respective resting contacts, opens the ring-back tone circuit for the calling subscriber at the normally closed contacts controlled by armature 228, and it completes the talking connection at armatures 228 and 231 and their respective front contacts.

Current is now supplied to the transmitter at substation A2 through the windings of the double-wound back bridge relay 201, which is accordingly energized. This relay is reversing relay and has the well-known function of reversing the incoming trunk conductors 138 and 140as regards their connections with the windings of relay 202. Relay 201 opens a point in the circuit Jfor the release magnet 210 at armature 213 and its resting Contact, and at armature 214 and its front contact closes an additional holding circuit for relays 206 and 208. The reversing of the line conductors 138 and 140 is a standard operation, and is for the purpose of operating a subscriber-s pay-station or metering apparatus, and in some cases is used for supervisory purposes. The desired connection is now completed and the subscribers may converse as desired.

When the conversation is completed the two subscribers replace their receivers. Should the calling subscriber restore his receiver first. the line relay 202 will deenergize and open the circuit of the slow-release relay 203. Relay 203 subsequently deenergizes and removes the ground from conductor 139 at armature 220 and its front contact, releasing the preceding switches in the usual manner. The connector 'C does not release due to the fact that the circuit for the release magnet 210 is open at armature 213 and its resting contact. The connector cannot be seized by any selector, such as selector S, because the battery potential is disconnected from conductor 139 at armature 244 and its resting contact. When the called subscriber hangs up his receiver, relay 201 deenergizes, removes the locking ground for relays 206 and 208 at armature 214 and its front contact, and closes a circuit for the release magnet 210 at armature 213 and its resting contact. Relay 206 deenergizes and opens a point in the locking circuit for wiper-switching relay 209. The slow-to-releaseswitch-through relay 208 subsequently falls back. Upon restoring to normal, switch-through relay 208 opens the locking circuit for the wiperswitching relay 209 at armature 250 and its frontv Contact, removes the locking ground for the combination switch-over and ring-cut olf relay 205 at armature 248 and its front contact, places battery potential on conductor 139 at armature 244 and its resting contact, removes the ground potential from the test wiper at armature 245 and its front contact, and opens the speaking connection at armatures 243 and 251 and their respective front contacts. The wiper-switching relay 209 deenergizes and connects up the normally connected wipers. The combination switchover and ring-cut-otf relay 205 subsequently falls back and the switch is restored to its normal position. The switch-through relay 208 is made slow-to-release to prevent the wiper-switching relay 'from releasing and connecting up the normally connected wipers before the switch shaft has restored the wipers to their normal position. lf the called party hangs up first the connector C is then released under control of the calling party.

It will be assumed that the calling subscriber desires to establish a connection with substation A1, whose telephone number is 3134. The setting up of the connection is exactly the same as described in establishing a connection with substation A2 whose telephone number is 3234, except that the second digit dialled is a 1 instead of a 2. The first digit (1) dialled into the connector (the second digit of the telephone number), locks up two-step-relay 206 as before. In this case only one impulse is transmitted; therefore, the wiper-switching relay 209 is not energized. The connection is then completed as previously described, but in this case over the normally connected wipers of the switch.

It Vcan be readily seen that the first digit (1 or 2) dialled into the connector C selects the set of wipers over which the connection is to be established.

A detailed description of the operation which takes place when the subscriber at substation A calls the party line subscriber B6,

shown in Fig. 4, whose telephone number is 2634 will now be given. When the calling subscriber removes his receiver and dials the digit 2 the operation of the lineswitcli LS and the selector S is exactly the same as described hereinbefore, except that the wipers 127-129, inclusive, of the selector S are positioned to the second level of the selector bank contacts to engage the bank contacts to which the conductors 141-143, inclusive, are connected.

In response t0 the seizing of connector C1 over the line conductors 141 and 143. the line relay 302 and the release relay 303 are energized. The operation of the line relay 302, release relay 303 and series relay 304,

is the same as describedin connection with line relay 202, releaserelay 203 and series relay 204 in. theeonneetor C, shown Fig. 2

contact, armatures 341, 349 and 330 andtheir respective resting jeontacts, normally closed contacts 335 of the vertical oi'inormal springs VGN, Winding' of magnet 363 of the auxiliary switch AS, to battery. In response tothe sin impulses over this circuit the Wipers 3711 and 372 of the auxiliary sWitchAS are :advanced step-by-step; to the sixth contacts aol? theirrespective' banks. yAt the end lof the series of'iinpulses', sericsrelay 304 deenergizes and completes ya circuit from battery, .lower Winding ci thezcombinationswitehecver and ,V ringecu90E relay-305, normally closed contact 327 of the Vertical oli-normal vsprings VGN, armature v326 and its resting Contact, Wiper 371 and the sixth bank contact oit the auxiliary switch AS, upper Wind-ingof the reyersino relay 306, upper Winding` cfwviper switching relay 300, armature 321 audits front Contact, to ground. Relays 305, 306, and 309 energize `over the above circuit. Upon energizing, relay 306,1at its lightly justed armature33 closes aloclring` circuit for itself from'hattery, resistance 366, arma ture .333 and its tront contact,lower Winding of relay 303, armature 321 and its front con tact, to ground. At armatures336 and 337 y; and their respective front contacts, relay306 prepares the circuit for transmitting ringing' curremtl over the lowerline conductor. Upon energizing, theV Wiper swltch'ing relay 309 closes a locking circuit vtor itself at itslightly fj adjusted armature 354,from battery, lower Winding of 'relay 5309, armature354 andV its front Contact, normally'closed contacts con: troiled by armature350,.armature 321 and its front contaeuytoground` At armatures 352,

- 353, 355 and'ftheir respective front contacts, relay 309 connects up the normally die connected Wipers BGG-362, inclusive. The combination switch-,over and ring-cutof` relayA 305, upon energizing, i prepares af locking t circuit tor itself at armature 329 and itsifront contact, and it alsoiprepares the circuit for the vertical magnet 311 atarmature330and its rontcontac 'lhegclosing of armatures and 331 andtheir respective 'front conf The calling subscriber maynow dial the 'third digit'of the called.number.V Whenthe t iird digit isdialled, which inltliiscaseisthe digi-t3, the circuit of the line `relay-302is again,intermittently interrupted three times ,252662, inclusive, p ande-are finally brought tores@ in engagement' in response to the operation ofthe calling de= vice bythe calling line relay 302 falls back, series relay 304 energizes `andl remains in an energized position-"throughout the series of impulses as has been hereinbefore described.- ing,.serics relay-304 opens the initial energiz= ing circuit for the Aslow-acting combination switch-over and ring-cutoff relay 305ga-tarm= ature 320 and its'resting` contact and by the same' action it also completes arlocking, circuit for relay 305 before it falls back, :trombate tory, lower Winding of relay 305, ,armature 329;. and its front contact, normally,closed contacts controlled by armature 348, armaa ture 326 and its frentcontaet over theprevi ouslytraeed circuit which includes the-upper windings of relays 306 and 309, respectively, to ground at armature 3 21 and its front contact, Asl a further result of the fall-ingback of line relay the Vertical magnet 311, from ground, armature318 and its resting contact, armature 323 and. its front contact, armatures 341 and 349 and their respective resting contacts, armasubscriber. The `first time .Upon energiza 302 a circuit is completed for taire-330,v and its front contact, Winding ofthe vertical magnet 311, `to battery.A "Each time the line relay 302 falls baekthis circuit is completed to the Verticalv magnet 311. the operation of the Vertical magnet 311, the Wipers 357-362, inclusive, are raised opposite the third level ofthe bank` contacts.

final digitofthe called telephone number,

Which-is in this ease thedigit 4, Responsive to Vthe interruptions,` of the line relay 302, series relay 304` is energized again and re'- mains energized throughout-theseries 'of iniv pulses. Each time line relay 302 falls back acircuit is completed for the-rotarymagnet 312.1from. ground,- armature 318 and its resting: contact, armature 323 and its front con# tact, 1 armatures 341- andx349 and' their respeetive resting contacts, armature 330 andits resting contact, eontacts334- ofthe rvertical oil-normal springs VON" (closed onft-hefirst vertical step of the switch), Winding ofthe rotary magnet 312, tobatteiy Byzthe opera# tion of :the roi-ary magnet' 312 the wipers areffctated stepsbyfstep at armature330 andlt's i thati-ts initial ener f' with the particular 4set of blank contacts to which the line of substation B6, whose telephone number is 2635, is terminated.

The series -relay 304 in its operated position Vconnects the test wiper 361 to the. two.

step-busy-test relay 307. If any of the contacts the test wiper 361 passes over are busy, the conductor similar to conductor 364 is grounded, causing the two-step-busy relay 307 to be energized in its first step from y ground (over a conductor similar to conductor. 364), test wiper 361, armature 363 andv its .front contact, normally closed contacts controlled by armature 345, normally closed contacts controlled by armature 339, armature 325and its front contact, armature 346 and its resting contact, resistance 332, winding of relay 307, torbattery. This relay is only momentarily operated to its rst step and closes contact A at armature 340 only, as

the test wip-er 361 passes over contacts of the busy lines. The operation of the relay to its first step has no eifect at this time because the circuit for energizing the relay toits second step is opened kat the normally closed contracts' controlled by armature 325 of theseries relay 304.

The final digit has nowbeen received and the wipers of the connector have been placed in connection with the terminals of the called step, from grounded conductor 364, test w1per361, armature 353 anditsrfront contact, normally closed contacts controlled` by armatures 345 and 339, respectively, normally closed contacts controlled by armature 325, armature 340 and its front Contact A, Awinding of relay 307, to battery. Upon energizing to its secondstep thel busy-test relay 307 opens the circuit for the rotary magnet 312 at armature 341 and its resting Contact to'prevent further rotation of' the wipers, locks itself at armature 339 and its front con- -tact to ground at armature 321 vand its front contact, at the same time opening its initial energizing circuit 4over'the test wiper 361, and it connects the busy tone conductor to the upper line conductor at armature 338 and itsfront contact. 'The subscriber, upon hearing the busy signal, will replace his receiver, thereby releasing the connector C1 and all previously operated switches.4

HavingV explained thev operation -which takes place when the called line is busy it will Vnow be -assumed that the called line is idle `when the connection is established.

` Under these circumstances there will be no ground on conductor 364 and consequently the busy test relay 307 will not be energized. Shortly after the last impulse of the series the series relay 304 falls back and completes the circuit for the slow-acting switching relay 308 from ground, armature 321 and its front contact, armature 339 and its resting contact, upper winding of switching relay 308, armature 367 and its resting contact, normally closed contacts controlled by armatures 325, 339, and 345, respectively, armature 353 and its front contact, test wiper 361, conductor 364, and thence to battery by way of the bridge cut-ofi winding of the lineswitch magnet ofV the associated lineswitch (not shown), which lineswitch may be the same as the lineswitch LS associated with the line of the substation A. Responsive to the closure of this circuit the lineswitch magnet ofthe called lineswitch operates its bridge-cut-oi armature to disconnect the line relay of the lineswitch from across the line conductors thereat..

In the connector C1 the slow-acting switching relay 308 energizes over the above traced circuit and at its lightly adjusted armature 347 closes a locking circuit for its lower winding from ground at armature 321 and its front contact, opens the circuit for the rotary e magnet 312 at armature 349 and its resting contact, and places direct ground on the test wiper 361 atarmature 345 and its front contact, and by the same action opens its initial energizing circuit. Relay 308 also prepares a locking circuit for the combination switchover and ring-cut-off relay 305 at armature 348 and its front contact, connects the ringback-tone conductor to the calling line at armature'342 and its front contact to indicate tothe calling subscriber that the calling line is being signalled, and it connects up the line wipers 360 and 362 at armatures 343 and 351 and their respective front contacts. By the latter operation, a signalling circuit is established whereby ringing current from conductor FREQ.` 3 is intermittently projected over the calledline to operate the ringer at the substation B6 to notify the called subscriber that he is wanted. The signalling circuit for the called subscriber is as follows: From the battery connected generator GEN,v ringing interrupter RING INT., conductor FREQ. 3 connected to switch j ack 3 of the connector, sixth contact of the bank associated with wiper 372, wiper l372, upper winding of the combination switch-over and ring-cut-otf relay 305, armature 336 and its front contact, armature 331 and its resting contact, armatures 351 and 355` and their respective front contacts, wiper 362, conductor 365, and the ringer at substation B6, to ground. The above circuit is; intermittently opened and closed by the operationV of the ringing interrupter RING INT. and the ringer at substation B6 is thus assenze K lrnown practice of harmonic signalling, and

it follows that the ringer at substation B6 is the onlyone which is operated. Y.

. When the called subscriber at substation B6 removes his receiver to answer the call, the ringer thereat isdisconnected and the ringing circuit is completed over a circuit including the other line conductor 363, wiper 360, armature 352 and its front Contact, arinature 343 and its front contact, armature 328 and its resting ccntact,;arinature 337 and its front-contact, to grouund. The combination switch-over and ring-cutoff relay 305 energizes overv this circuit and closes a locking circuit for itself its lightly adjusted arm-V ature 329 and itsjfront Contact, from ground at armature 343 and its front Contact, through thelower winding of relay305 to battery. Relay 305 also opensitsoriginal energizing circuit at armatures-323 and 331 and their respective resting contacts and atthe saine time completes a talking connection at their respective front contacts, and by the same action disconnecting the 'ring-baclr-tone conductor troni the upper line conductor 141.

Current is now supplied to the transmitter at substation Btl 'through the windings of the double wound baclebridge relay 301, which is accordingly energized. This relay isa rcversing relay and has the well lrnown function of reversingthe lincoiningf trunl; con duc-tors 141 and `143, as regards their'connections with the windings of line relay 302. Relay 301 opens a point in the lcircuit tor release magnet 310 at armature 3l3 and its resting Contact, and at arniaturej3`l4 and its'tront contact closes an "additional holding circuit for relays 306 and 303. The reversing of the line conductors 141 and 143 is a standard operation, and is Jfor the purpose oi operating a subscribers paystation or metering apparatus, and in Sonie cases is used tor supervisory'purpcses. The desired connection is now completed and the subscribersmay converse desired. f Y

'When Athe conversation `is completedthe two subscribers replace their receivers. The releasing of the connection is controlled by the calling and the calledsubscriber in the saine manner as described in connection with the connector C shown in Fig. 2. However, an additional circuit is provided under the control ot release relay 303 which is closed when theV calli subscrib'erhangs up his receiver to restore the auxiliary switch hte its nornial position. The circuit for releasing the auxiliary switchl-LS isasfollows ground,

armature 371 and its resting contact, olii-normal springs 36,9 of `the auxiliary switch-51S (closed on the lirst rotary step of its wipers 371-.37 2) winding of the release magnet 37 0 o1 `the auxiliary switch AS, to battery. All the apparatus used in establishing a connecticnisv thus released andl may be usedin the establishment ot another connection.

i An explanation will now be given of the manner in which connectionsare established with the other tour substati ons on this party line. The substations B7, B3, B9, and B10, shown in Fig. 4, inay'be reachedbydialling .2?34, V2334, 2934, and 2034, respectively. lt will be `noted that the `tiret, third, and fourth digits ot the telephone nuinl erl are exactly the saine as used in calling substation B6.

. When the digit 7 is dialled t'or the second digit ot a telephone nuinber the'conibination switch-over and ringcut-oliY relay 305 and the `wiper switching relay 309 are, energized in series overthe previously described circuit which now includes the seventh bank contact associated with wiper 371. :lt will be noted that relay 306 is not in this circuit, therefore, FREQ.. 4 will be transmitted over the upper line conductor to subscriberB? whose ringer is shown connected to the upper line condu@ Vtor 363, Fig. 5,

Should the calling subscriberdesire" to converse with the substation'BS theseccnd digit of the telephone number would be the digit 3. In this case the wipers 371-372 of the auxiliary switchAS are advanced to the eighth bank Contact. The operationof the switch in this case `will' be exactly thesanie as described in Aconnection with a call for substation BG, except that FREQ. 4 is transmitted over the lower line conductor to subscriber B8 whose ringer is shown connected to the lower Vline conductor 365, Fig. 4.

I n establishing a connection to substation B9 or B10 the second digit ot the telephone number would befeither 9 or 0.` It substation B9 is dialled the wipers {1371*372 of the auxiliary switch AS are advanced tothe ninth bank contact. Thefoperation of the circuit in this case is exactly the sameas disclosed in connection with the description of establishing a connection with substation B7, except in this case FRE@ 5 is transmitted over the upper line conductor toV subscriber B9 whose ringer is shown connected to the upperlineconductor 363, Fig. 4..

In establishing a connection to Vsubstation 7 B10 the wipers of the auxiliary switch ,AS are advancedto the tenth bank` Contact when the digit is dialled. The operation of the circuit inlthis case is the saine as described in connection with establishing a connection with substations` B6 and B8, respectively, except in thisA case FREQ. is transmitted over lower line conductor to subscriber B whose ringer is shown connected tothe lower line conductor 365, Flg. 4.

An explanation will now be givenof the manner in which a connection is established with substation B5, as shown in Fig. 4. The substation B5 may be reached by dialling f 2534 and it will be noted that the first, third and fourth digits of the telephone number are exactly the same as used in calling substations 13G-B10, inclusive. Vhen a calling subscriber removes his receiver` and dials the digit 2 the operation of the lineswitch LS and the selector S, shown in Fig. 1, is exactly the same as described hereinbefore. The connector C1 is seized in the regular manner over conductors 141 fand 143, operating the line relay 302 and the release relay 303, as has been'described.

The calling subscriber may now dial the second digit of the called number, which in this case is assumed to be the digit 5. Each time the line relay 302 falls back a circuit'is closed to magnet 368 of the auxiliary switch AS. In response to the five impulses magnet 368V' advances its Wipers 371 and 372 to the fifth contacts of their respective banks. At

' the end of the series of impulses, series relay 304 deenergizes as before and completes a circuit from battery, y'lower winding of the combination switch-overand ring-cut-ofli1 relay 305, normally closed contacts 327 of the vertical oH-normal springs VON, armature 326 and its resting contact, wiper 371 and the fifth bank contact of thezauxiliary switch AS, armature 321 and its front contact to ground.

The combination switchover and ring-cutoff relay 305 energizes over the above cir-cuit and prepares a locking circuit for itself at armature 329 and its front contact, and at armature 330 and its front contact prepares a circuit for the vertical .magnet 311. The closing of armatures 328 and 331 and their respective front contacts has no effect at this time.

The calling subscriber may now dial the third and fourth digits of the called number. When the third and fourth digits are dialled, which in this case are the digits 3 and 4, respectively, the wipers 357-362 are raised opposite the third level of the bank contacts by the operation of the vertical magnet 311, and are rotated in to the fourth bank contacts by the operation of the rotary 'magnet 312, as has been hereinbefore described.

It should be noted at this time that the wiper switching relay 309'has not been operated, therefore, the connection will be established over the normally connected set of wipers 357-359, respectively. AThe, final digit has now been received and the wipers of the connector have beenl placed maconnection with terminals of the called line. If Vthe line isbusy, there will be aground potential on the test conductor'374, which completes a circuit for operatingthe twostep busy'test relay 307 toits first step before the Series relay 304 falls back aftertheseries of'impulses. I ,Series relay 304 subsequently releases, however, and at the normally closed contacts controlled by armature 325 it completes a circuit for energizing relay 307 to its seco-nd step, from grounded conductor 374, test wiper 358, armature 353 and its front contact, normally closed contacts controlled by armatures 345, 339, and 325, respectively, armature .340 and its front contact A, Winding of relay 307, to battery. Upon energizing to its second step the busy test relay 307` opens the circuit for the rotary magnet 312 at varmature 349 and its resting contact to prevent further rotation of the wipers, locks itself at armature 339 and its front contact'to ground at armature 321 and its front contact, and at the same time opens its initial energizing Ycircuit over the test wiper 358, `and it connects the busy tone conductor to the upper line conductor at armature 338 and its front contact. The calling subscriber, upon hearing the busy signal, will replace his receiver thereby releasing the connector C1 and all previously operating switches. f i

Having explained the operation which takes' place when the called line is busy 1t will now be assumed that the called line is idle when a connection is established. Under these circumstances there will be no ground on conductor 374 and the two-stepbusy-test relay .307 will not be energized. Shortly after the last impulse of the series, the series relay 304 falls back and completes the circuit for the slow-acting switching relay 308 from ground, armature 321 and its front contact, armature 339 and its resting contact, upper winding of the switching relay 308, armature 367 and its resting contact, normally closed contacts controlled by armatures 325, 339, and 349, respectively, armature 353 and its front contact, test wiper 353, conductor 374, and thence to battery by way of the bridge-cutoff winding of the lineswitch magnet of the associated lineswitch (not shown), which lineswitch may be the same as the lineswitch LS associated with the line at the substation A, shown in Fig. 1. Responsive to the closure of this circuit the lineswitch magnet of the called lineswitch operates its cut-off armature to discoimect the line relay of the lineswitch from across the line conductors thereat. f

In the connector C1 the slow-acting switching relay 308 energizes over the above traced circuit and at its lightly adjusted armature 347 closes a. locking circuit for its lower windingfrom ground at armature 321 and its front contact, opens the circuit'for the rotary magnet 312 at armature 349 and its resting contact, and places direct ground on the testwiper 358 at armature345 and its front contact, and'by the same action opens its initial energizing circuit. Relay 308 also prepares a locking circuit for the combination -switchfover and ring-cutoff` relay 30.5 'l

at armature 348 and its front contact, connects the ring-back--tone conductor` to the calling line at armature 3412 and its front Contact te indicate to the call-ingv subscriber thattlre calling lin-e is being signalied, and it connects up the line wipers 357 and 359 at armatures343 351 in their respective front contacts. By thelatter operation, a signalling circ-uit is established lwhereby ringing current from conductor FREQ. 3 is intermittently projected over the called line to opera-te the ringer at the substationiB5 to notify the called subscriber .that he is wanted. The signalling circuit for the called subscriber is as follows: rom the battery connected generator GEN, Vringing interruptor RING INT, conductor FBEQ. 3 connected to switch jack 3 of the connector, fifth contact of the bank associated with wiper`372,l Wiper 37.2,upper winding of the switch-over and ringscutfo relay 305, armature 336 and its resting Contact, armature 328 and its resting contact, armature 343 and its V,front Contact, armature 352 and its resting contact,rwiper 357, conductor `373, and the ringer at substation B5, to ground. The above circuit is intermittently/'opened and closed by the operation of the ringing interrupter RING IN T and the ringer at substation B5 is thus operated at intervals tosignal the called subscriber. It is understood, of course, that the ringing current also iiows through `the ring.- er at substations Bl and B3, shown in Fig. 4,

. to ground at the same timebut the ringers thereat are tuned so that they `will notrespond tothe frequency of ringing current Whichis now in use.` This is in accordance with the wellV known practice of harmonic signalling', and it follows that the ringer at substation B5 is the only one which is operated.

mien the called subscriber at `substation B5 removes his receiver to answer the call, the ringer thereat is disconnected and the ringing circuit is completed over a circuit including the other line conductor 375, wiper 359,. armature 355 and its resting contact, armature 351 and itsfront contact, armature 331 and its resting contact, armature 337 and its resting contact, to ground.` The combination switch-over and ring-cutsoi' relay 305 energizes over this circuit closing locking circuit for itself at itslightly adjusted arma-ture 329 and its front contact,

.from ground at armature 348 and its front contact, through the lower winding of relay 305 to battery, Relay 305 also opens its original energizing circuit at armatures 328 and 3.31 and their respective resting contactsand at the same time completes a talking connection at their respective front contacts, and by the same action disconnecting the ringbaclrrtone conductor from the upperline conductor 141.. The release ofl the apparatus establishing the connection is the same as has been hereinbefore described.

An explanation will now be given of the. `manner in which connections are established with the other vfour substations on this party line, The substations B1, B2, B3, and B4,

shown in Fig. 4, maybe reached by vdialling 2134, 2234', 2334 and 2434, respectively, It 'will be noted that the first, third, ,and fourth digits of the telephone numbers `are exactly the same as used in' callingsubstations B5-B10, inclusive. Y i

When the digit 1 is dialled as the second digit of the telephone number the auxiliary switch AS positionsits wipers 371 and V37.2 to the first contacts of its associated .banks which transmits FREQ. 1 over the line condnctor 373 to operate the ringer atsubstation Bl. If the digit3 is dialled .as the second digit the auxiliaryjswitch AS will position its wipers 371 and 372 to the third bank Contact, and in this case FREQ. 2 yis transmitted over the line conductor 373 to substation B3. Y

If the second digit of the called number is either 2 or 4 the wipers .371 and .372 of the auxiliary switch AS will be advanced tothe second or fourth -contacts of their associated bank. The circuit for the 4cornbination switch-over and ringcut-oif relay 3.05 will then include the lower winding .of the .reversing relay 306 over the following circuit :f Battery, lower winding of relay 305, contacts 327 ofthe vertical off-normal springs VON, armature 326 and its resting contact, wiper 371of the auxiliaryfswitch AS, and the second or fourth contact of its associated bank contact,y lower winding of the reversing relay 306, armature 321 `and its `front Contact, to ground. Relays .305.and

306 energize over this` circuit., upon energizing, closes a locking circuit for itself from battery, resistance: 366, armature 333 and its front contact, lower winding of relay 306, armature 321 and itsfront contact, to ground and at armatures v336 and 337 and prepares a .circuit for transmitting FREQ. 1 or FREQ. 2 over the lower line conductor 3.75.,.through the ringer of substations B2 or B4.

Relay 3.06`

vThen tenparty service is desired, the

same group` of connectorsserving the fiveparty lines, shown in Fig. 4, may be used fory selectively signalling the subscribers connected :to vthe ten-party line shown, in Fig. 5, One of the frequency selecting connectors of the group is the connector C1 shown in. Fig. 3 and the different ringinggenerators are connected Ato the 'switch jack Vterminals of the connector as shown tothe, left of Fig. 5( By multipling the party line conductors to two sets of bank fcontactsaccessible tothe two sets of wipers of theconnector G1, the subscribers (ll-C5 are selectheir respective front contacts itwiththe bank contact-sv to scribers (I6-C10 are selectively signalled when the normally disconnected set of wipers ofthe connector are associated with the bank contacts to which the conductors 563- 565 are connected. The si nailing of a particular subscriber on the line is exactly the same as has been explained in connection with Fig. 4,. l hen three party service is desired, a group of frequency selecting connectors,

r (similar to the connector C1), having the different ringing current generator leads wired to the switch jack terminals, as shown to the left of Fig., 6,.are used. It will'be noted that only threerdifferent ringing frequencies are required' forV selectively signalling theparties of the two three-party lines shown in Fig. 6. The telephone members of the connected subscribers are the same except for .the second digitof'the number which selects the vringing frequency, the set of wipers, and the side ofthe line over which Athe ringing current is tobetransmitted.

vIt is assumed that the frequency selecting connector C1 shown in Fig.3, is one of a group .of connectorshaving the switch jack terminals wired as shown to the left of Fig. 6, and that the second digit of the called number is 1, 3, or 5. In response to the dialling of any of these digits as the second digit of the called number the wipers 371 and 372 of the auxiliary switchAS are advanced to contacts 1, 3, or 5 of their associated banks. With the auxiliary switch wipers on any one of these contacts the normally connected set .of wipers 357-359 of the connector C1 are used and the ringing frequency. (FREQ. 1, FREQ. 2, or FREQ; 3) selected by wiper 372 of the auxiliary switch A S is transmitted to subscriber D1, D3, or D5 over` the following circuit: battery connected generator GEN, ringing interrupter RINGINT., conductor FREQ. 1, 2, or 3 connected to switch jack v.1, 2 or 3, respectively, wiper 372 of the auxiliary switch AS and its lassociated ybank con'- tact 1, 3, or 5, upper winding of the combina- Ltion switch-over andv ring-cut-o relay 305, armature 336andfits resting contact, armature 328 and its resting contact, armature 34:3 and its front contact, armature 352v and its resting contact, wiper 357, y conductor 673 (Fig.v6) ringer of substation D1, D3, or D5 "(depending on the selected ringing frequency) conductor 675, wiper 359, armature 355 and its resting contact, armature 351 and Vits front contact, armatures 331 and 337 and their respective resting contacts, to ground. The above circuit is intermittently opened and closed by the operation of the ringingv interrupter RING INT. and the ringer at the selected substation is operated at intervals I to signal the called scrisse subscriber. y It is understood, of course, that the ringing current also flows through the ringers at'the other substations on the line, but the ringers thereat are tuned so they will not respond to the frequency of the ringing current which is now in use. This is according to the wellknown practice ofharmonic signalling, and it follows that the ringer at the selected substation is the only one which is operated.

Vhen the called subscriber responds to the ringing of his bell by'rernoving his receiver, a direct current bridge is closed across the associated line conductors 673 and 675 in the regular manner, whereupon the ring-cut-off relay 305 energizes. The operation of the circuit following 'the energization of the combination switch-over and ring-cut-o relay 305 is exactly the saine as has been hereinbefore described.

In order to establish' a connection with subscribers D6, D8, or D10, connected to the other three-party line shown in Fig. 6, and whose ringers are bridged across conductors 663 and 665, the second digit of the called number is either 6, 8, or 0. The first, third, and fourth digits of the telephone number are the same as used in establishing a connection with subscribers D1, D3, or D5. The wipers 357-362 ofthe modified connector C1 are connected to the conductors 663-665 and 673-675, shown in Fig. 6 over their associated banky contacts and the wipers 371 and 372 cf theauxiliary switch AS are advanced to lcontacts 6, 8, or 10 of their associated banks by the second digit of the called number. WVith the auxiliary switch wipers 371 and 372 on any one of these ycontacts the reversing relay 306 and the wiper switching relay-,309 of the connector C1 will be ener gized. With the wiper switching relay 309 energized the normally disconnected' set of wipers 360-362 is used for completing the connection over conductors 663-665 to subscribers D6, D8, or ing frequency FREQ. 1, 2, or 3 is transmitted to subscribers D6, D8, or D10, over the following circuit: batteryv connected generator GEN, interrupter RING INT, conductor FREQ. 3, 2, or 1, connected to switch jack 3, 4, or 5, respectively, wiper 372 of the auxiliary'switch AS' and its associated bank contact 6, 8, vor 10, upper winding of the combination switch-over and ring-cut-oiil relay 305, armature 336 and its front contact (relay 306 having been energized over wiper 37 2V and contact 6, 8, or 10 of its associated bank) armature 331 and its resting contact, armatures 351 and 355V and their associated front contacts, wiper 362, conductor 665 (Fig. 6), ringer at substations D6, D8, or D10 (depending on the selected ringing frequency), conductor 663, wiper 360, armatures 352 and 343 and their respective front contacts, armature 328 and its resting con- D10. The selected ring "assenze tact, armature 337 and its front contact, to ground. The ringer at the selected substation is tuned to respond to a particular ringfrequency. r

When the called subscriber responds to the ringing of his bellr by removing his receiver, ay direct currentl bridge is closed across the associated line conductors 363- and 365 in the regular manner, whereupon thev ring-cutoil relayjSO energizes-` The operation of the circuit following theenergization ofthe coin` bination switch-over land ring-cut-oi relay 395 is exactly the saineas has been'herein- `"before described.

lt should be Ynoted that the digit of the number for calling subscribersDl, D3, D8, and B can be "either digit l or 2 for subscriber D1, digit 3 or 4 forsubscriber D3, digit 7 or S for subscriber' D8, and digit 9 or 0 for subscribed B-l0. In case the digit 2 or l yis dialled the ring reversing relay 306 is operated over the second or fourth bank Contact ot the auxiliary switch AS." The saine subscriber, D1 or D3, is signalled by the saine ringing frequency as' in the case when digit l or 3 was dialled, however, the ringing current is nowtransniitted over the opposite line conductor and back to ground atarinature 337 of the reversing relay 805. The ringer at the wanted subscribers station responds and theconnection is coinpleted as before. ln case the digit 7 or 9 is dialled'tlie ring-reversing relay isnot operated, as is the case when digits 6, 8, or 0` are dialledasthe second digit, however, the wiper switching relay 809 is operated as before over the seventh and ninth bank contacts of the auX- iliary switch AS. The saine subscriber, D8

or D10, is signalled by the saine ringing frequency as iii the case when digit'S or Olwas dialled, however, lringing curren-t'is transinitted overl the opposite line conductors. The ringer at the wanted subscribers station responds and the conversation is'complet-ed` in the regular inanner.

The saine group of frequency selecting connectors servingthe two three-party lines in Figs. 6 can also be used for establishing connectioiis with five-party lines, such as the two five-party lines shown in Fig. 7. t is-assuined that'the frequency selecting connector C1 shown inllig. 3, is one of a groupvof connectors having the switch jack terminals wired as shown to the left of F ig. 7. lt will be noted that three `different Yringing fre-v quencies are wired to the switch jack ter- Mininals in the saine inanner in Figs. 6 and 7,

therefore, the saine group of connectors inay be used for establishing connection' with subscribers connected to three or five party lines. The Vtelephone number of the subscribers connected to the two five-party lines shown inFig. 7 isthe same except for the second digit ofthe number which selects the ringing frequency, the set of wipers, and the side of the line over which ringing 'current is to be transmitted.

The signalling of subscribers El-ElO, inclusive,shown in Fig. 7, is the saine as described for signalling subscribers Bl-BlO,

of diilerent resistances for each of said lasty two. relays, contacts on saidline relay for closinga circuit when said lineA relay is-operated, saidfcircuit including the low and high resistance windings of said release relay and one winding of said series relay in series,. self locking contacts on said release relay nfor closing a loosing circuit for maintaining said Vrelease relay operated, other contacts for closing a circuit to the other winding of said series relayin series with said lo resistance winding of said release relay to operate said series relay, and contacts on saidA line relay for completing a shunt cir'- ycinltaround the high resistance winding of Vsaid release relay to inalre it slow to release whereby said release relay operates the first time said line relay is energized and remains operated during successive operations of said line relay. l

2. ln an automatic switch, a line relay, a release relay, a change-over relay, two windings for each of said relays, inea-ns for operating said line relay, contacts closed respon- -e to the operation of said line relay for operatingsaid release relay, and contacts closed-responsiveto the operation of said release relay for operating said change-over relay in series with one winding of said release relay. y y

3. ln an automatic switch, a line relay, a double wound release relay, a double wound change-over relay, va circuit for operating raid line relay, a irst circuit for operating said release relay over both of its windings in series with one winding of said changeover'relay, asecond circuit for operating said change-over relay `over both its windings in series with one winding of said release relay, a fourth circuit "for shunting one winding of said release relay when said line relay inoinentarily falls back, and contacte on said line relay for opening the circuit of one winding ofsaid change-over relay, current flow in said release .and Vchange-over relays being sulicient to maintain said lrelays in an energized position during tlieinoinentary interruptions of said line relay..y

tra

lio

4. In an automatic switch, a line relay, a double wound release relay, a double wound change-over relay, a circuit for operating said line relay, a first circuit for operating said release relay over both of its windings in series with one winding of said changeover relay, a second circuit for operating said change-over relay over both its windings in series with one winding of said release relay, a fourth circuit for shunting one winding of said release relay ywhen said line relay momentarily falls back, contacts on said line relay for opening the circuit of one winding of said change-over relay, current flow in said release and change-over relays being suflicient to maintain said relays in an energized position during t-he'momentary interruptions of said line relay, and off-normal springs operated if said switch is olf-normal to prevent said first circuit from being completed.

. 5. In an automatic switch, a line relay, a release relay having two windings, a series relay having two windings, a circuit for operating said line relay, a first circuit for operating said release relay over both o f its windings in series with one winding of said series relay when said line relay is operated, a second circuit for operating said series relay vover a second winding of said series relay in series with one winding of said'release relay and for making said release relay slow-torelease when said line relay has momentarily deenergized, and a third circuit for operating said release relay over said first circuit and for making said series relay slow-to-release over a circuit including both windings of said release relay in series with the other winding of said series relay when said line relay is again operated.

6. In an automatic switch, a wiper-switching relay, a two-step relay operated through its first step to close a locking circuit for itself which operates the relay through its. second step when its initial energizing circuit is opened, contacts on said second relay for pre* paring a circuit to said wiper switching relay, a normally connected set of wipersand a normally disconnected se't of wipers, and contacts on said wiper-switching relay for disconnecting the normally connected .set of wipers and for connecting the normally disconnected set of wipers when saidv relay is operated. n

7. In an automatic telephone system,.an impulsing device, anautomatic switch operative responsive to a plurality of series of impulsestransmitted by said impulsing device,

a 'two-step relay operated through its first step by the first impulse of the first series, contacts on said relay for operating it through its second step when said first impulse of said first series is terminated, a normally connected set of wipers and a normally -disconnected set of wipers, and a wiper switching relay operated by the second impulse of the first series to connect the normally disconnected set of wipers.

8. In an automatic switch, a two-step busy test relay, a first circuit for operating said relay through its rst step to close one pair of its contacts when saidv switch encounters a busy line, and means for operating said relay through its second step over a circuit including said pair of contacts and the busy line when its-initial energizing circuit is opened.

9. In a connector, a test wiper, a two-step busy-test relay, a circuit including said test wiper for operating said relay in its first step, and a circuit including said test wiper 'and contacts closed by the relay in its first step for operating the relay in its second step.

10. In combination, a connector switch, a plurality of sets of wipers, an auxiliary switch individual to said connector switch, means for cont-rolling said auxiliary switch,

'a plurality of signalling currents, and wipers controlled by said auxiliary switch for select- Ving a particular one of said signalling currents, one of said'plurality of sets of wipers, and the side of the line over which said sig nalling current is to be transmitted.

11. In a switching device having a plurality of sets of wipers for extending connections to party lines, means for selecting a particular set of wipers and the signalling current for signalling a particular party on a line and for thereafter selecting the desired line, and a relay controlled by said first selecting means for determining over which Vside of the line the signalling current is to be transmitted.

12. In a telephone system, a connector switch having a plurality of sets of wipers, each set of wipers having access to a plurality of party lines, an auxiliary switch individualto said connector, a plurality of sources of ringing current, means controlled by said connector for operating said auxiliary switch to select a particular one of said sources of ringing current, the set of wipers, and thevside of the line over which the ringing currentis to be transmitted, and means for thereafter connecting said wipers to a desired line.

13. In a telephone system, a plurality of lines, a connector having a plurality of sets ofwipers, an auxiliary switch individual to said connector, a plurality of sources of ringing current, means for positioning said auxiliary switch and for subsequently positioning said connector to select one of said lines, and means controlled byV said auxiliary switch for selecting one of said sets of wip-ers, one of said sources of ringing current and the side of the line over which the ringing current 'l is to be transmitted.

14. In an automatic telephone system, two party lines, a connector switch having a normally connected set of wipers and a normally disconnected set of wipers, means in said con- 

